From 28cb9fd4dc24522f772aa214bd0c4493bd1ff0d3 Mon Sep 17 00:00:00 2001
From: Adam Waldron <awaldron@brightcove.com>
Date: Tue, 16 Jul 2024 22:28:30 -0700
Subject: [PATCH] fix: fastQualitySwitch stability (#1525)

---
 src/playlist-controller.js       |  9 +---
 test/playlist-controller.test.js | 70 +++++++-------------------------
 2 files changed, 17 insertions(+), 62 deletions(-)

diff --git a/src/playlist-controller.js b/src/playlist-controller.js
index 1a32bb9b3..46708c829 100644
--- a/src/playlist-controller.js
+++ b/src/playlist-controller.js
@@ -1059,15 +1059,10 @@ export class PlaylistController extends videojs.EventTarget {
 
   runFastQualitySwitch_() {
     this.waitingForFastQualityPlaylistReceived_ = false;
-    // Delete all buffered data to allow an immediate quality switch, then seek to give
-    // the browser a kick to remove any cached frames from the previous rendtion (.04 seconds
-    // ahead was roughly the minimum that will accomplish this across a variety of content
-    // in IE and Edge, but seeking in place is sufficient on all other browsers)
-    // Edge/IE bug: https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/14600375/
-    // Chrome bug: https://bugs.chromium.org/p/chromium/issues/detail?id=651904
+    // Delete all buffered data to allow an immediate quality switch.
     this.mainSegmentLoader_.pause();
     this.mainSegmentLoader_.resetEverything(() => {
-      this.tech_.setCurrentTime(this.tech_.currentTime());
+      this.mainSegmentLoader_.load();
     });
 
     // don't need to reset audio as it is reset when media changes
diff --git a/test/playlist-controller.test.js b/test/playlist-controller.test.js
index ebded8451..a58e7aa3c 100644
--- a/test/playlist-controller.test.js
+++ b/test/playlist-controller.test.js
@@ -688,10 +688,11 @@ QUnit.test(
   }
 );
 
-QUnit.test('resets everything for a fast quality change', function(assert) {
+QUnit.test('resets everything for a fast quality change then calls load', function(assert) {
   let resyncs = 0;
   let resets = 0;
   let removeFuncArgs = {};
+  const done = assert.async();
 
   this.playlistController.mediaSource.trigger('sourceopen');
   // main
@@ -709,16 +710,24 @@ QUnit.test('resets everything for a fast quality change', function(assert) {
 
   const origResetEverything = segmentLoader.resetEverything;
   const origRemove = segmentLoader.remove;
+  const origLoad = segmentLoader.load;
 
-  segmentLoader.resetEverything = () => {
+  // ensure load is called
+  segmentLoader.load = () => {
+    done();
+    origLoad.call(segmentLoader);
+  };
+
+  segmentLoader.resetEverything = (doneFn) => {
     resets++;
-    origResetEverything.call(segmentLoader);
+    origResetEverything.call(segmentLoader, doneFn);
   };
 
-  segmentLoader.remove = (start, end) => {
+  segmentLoader.remove = (start, end, doneFn) => {
     assert.equal(end, Infinity, 'on a remove all, end should be Infinity');
-
-    origRemove.call(segmentLoader, start, end);
+    assert.ok(doneFn);
+    doneFn();
+    origRemove.call(segmentLoader, start, end, doneFn);
   };
 
   segmentLoader.startingMediaInfo_ = { hasVideo: true };
@@ -777,55 +786,6 @@ QUnit.test('loadVttJs should be passed to the vttSegmentLoader and rejected on v
   });
 });
 
-QUnit.test('seeks in place for fast quality switch on non-IE/Edge browsers', function(assert) {
-  let seeks = 0;
-
-  this.playlistController.mediaSource.trigger('sourceopen');
-  // main
-  this.standardXHRResponse(this.requests.shift());
-  // media
-  this.standardXHRResponse(this.requests.shift());
-
-  const segmentLoader = this.playlistController.mainSegmentLoader_;
-
-  return requestAndAppendSegment({
-    request: this.requests.shift(),
-    segmentLoader,
-    clock: this.clock
-  }).then(() => {
-    // media is changed
-    this.playlistController.selectPlaylist = () => {
-      const playlists = this.playlistController.main().playlists;
-      const currentPlaylist = this.playlistController.media();
-
-      return playlists.find((playlist) => playlist !== currentPlaylist);
-    };
-
-    this.player.tech_.on('seeking', function() {
-      seeks++;
-    });
-
-    const timeBeforeSwitch = this.player.currentTime();
-
-    // mock buffered values so removes are processed
-    segmentLoader.sourceUpdater_.audioBuffer.buffered = createTimeRanges([[0, 10]]);
-    segmentLoader.sourceUpdater_.videoBuffer.buffered = createTimeRanges([[0, 10]]);
-
-    this.playlistController.runFastQualitySwitch_();
-    // trigger updateend to indicate the end of the remove operation
-    segmentLoader.sourceUpdater_.audioBuffer.trigger('updateend');
-    segmentLoader.sourceUpdater_.videoBuffer.trigger('updateend');
-    this.clock.tick(1);
-
-    assert.equal(
-      this.player.currentTime(),
-      timeBeforeSwitch,
-      'current time remains the same on fast quality switch'
-    );
-    assert.equal(seeks, 1, 'seek event occurs on fast quality switch');
-  });
-});
-
 QUnit.test('basic timeToLoadedData, mediaAppends, appendsToLoadedData stats', function(assert) {
   this.player.tech_.trigger('loadstart');
   this.playlistController.mediaSource.trigger('sourceopen');